US3427967A - Method of printing with low condensate printing ink - Google Patents

Description

Feb. 18, 1969 1.. E. THIELEN 3,427,967

METHOD OF PRINTING WITH LOW CONDENSATE PRINTING INK Original Filed April 25, 1966 Sheet 0f 2 a n nvzu 'nvAvAvAvA FIGI / INVENTOR LAWRENCE E. THIELEN BY 1? M147 M (4%,

77 2 find. ATTORNEYS L. E. THIELEN Feb. 18, 1969 METHOD OF PRINTING WITH LOW CONDENSATE PRINTING INK Sheet Original Filed April 25, 1966 FAN M 33 K? BURNER FAN United States Patent 3,427,967 METHOD OF PRINTING WITH LOW CONDENSATE PRINTING INK Lawrence E. Thielen, Villa Park, Ill., assignor to R. R. Donnelley & Sons Company, a corporation of Delaware Continuation of application Ser. No. 544,965, Apr. 25, 1966. This application Nov. 13, 1967, Ser. No. 685,237 US. Cl. 101--211 2 Claims Int. Cl. B41m l/14 ABSTRACT OF THE DISCLOSURE A printing ink comprising a hydrocarbon soluble film forming resinous binder together with the solvent, pigment material and additives in which a least 98% of the ink is made up of ingredients that yield less than 6% condensate when measured by The Test Procedure described in the specification hereof with the result that the inks of this invention do not produce condensate streaks in letterpress and offset printing.

This is a continuation of my application Ser. No. 544,965, filed Apr. 25, 1966, now abandoned.

This invention relates to letterpress and offset heat set printing inks and to high speed rotary web fed letterpress and offset printing methods.

The formation of condensate streaks on printed paper has been a problem ever since heat set inks were first developed. In spite of many attempts to cure or alleviate this problem, it has up to now not been satisfactorily solved. The nature of the problem in question is explained as follows.

In heat set printing (both letterpress and offset) an ink is used which includes a pigment, a film forming hydrocarbon soluble resinous binder or drying oil, various additives and a hydrocarbon solvent. After the ink has been applied to the paper web the latter is passed through a dryer where the solvent is driven from the ink by the application of heat to the web.

The condensate streaks herein referred to may be discolored streaks on printed signatures which are made up of more or less oily, greasy, or tallowy or waxy material which has apparently been volatilized in the course of the drying process and has thereafter been condensed at relatively cool locations where sufficient material can accumulate to form, upon transfer to the printed web, the condensate streak-s in question. The condensate streaks may also take the form of streaks of resoftened and retransferred ink formed when drops of condensed ink solvent are transferred to the printed paper web where they soften the dried ink and cause its transfer to the opposed paper surface when the paper web is subsequently cut and folded. To explain more fully the formation of condensate streaks, it is necessary to describe in some detail the drying systems conventionally used in association with high speed web fed rotary letterpress and offset printing presses. Such a description is given hereinbelow.

One of the features of this invention therefore is to provide an improved printing ink which avoids condensate streaks in letterpress and offset printing.

Another feature of the invention is to provide an improved method of continuously printing on a moving paper web with a heat setting ink including the step of passing the freshly printed web through a heat setting zone having relatively cool areas without causing condensate streaking on the web.

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Other features and advantages of the invention will be apparent from the following description of certain embodiments thereof with the method of the invention being illustrated in several embodiments in the accompanying drawings which also illustrate an apparatus for measuring the condensate of the ink ingredients. Of the drawings:

FIGURE 1 is a fragmentary side elevational diagrammatic view illustrating one apparatus for conventional dryers for heat set printing.

FIGURE 2 is a view similar to FIGURE 1 but illustrating a second conventional dryer.

FIGURE 3 is a view similar to FIGURES l and 2 but showing a third embodiment of a conventional dryer.

FIGURE 4 is a diagrammatic vertical ymmetrical sectional view through an apparatus for measuring the condensate content of an ink ingredient.

The radiant cup dryer of FIGURE 1 includes a series of three open-bottomed, open-ended boxes 10 arranged in spaced, tandem relationship above the path of the printed web 11 moving in the direction indicated by the arrows from a first set of printing-impression cylinders (not shown), the web being supported while in said path by small internally water cooled idler rolls 12. Each box has supported therein an array of gas fired radiant ceramic burners 13 facing the web 11. The boxes 10 are interconnected by hoods 14 and the last box has connected to its exit end an exit hood 15. Each of these hoods has connected thereto a branch 16 of a main exhaust duct 17 provided with an exhaust. fan and a catalytic smoke burner (not shown). From the last of the support rolls 12 the web 11 passes over a pair of large driven internally water cooled chill rolls 19 to a second set of printing-impression cylinders (not shown) followed by a dryer essentially similar to that shown in FIGURE 1.

In the dryer of FIGURE 1, the temperature of the ceramic cups 13 in the radiant burners ranges from 900 F. to 1400 F. (within a single cup), and the web 11 exit temperature ranges from 450 F. to 550 F. The web speed may range from 1500 to 2000 f.p.m.

In the steam drum dryer of FIGURE 2, the printed web 20 passes from a first set of printing-impression cylinders (not shown) over a small infeed idler roll 21, around a large (6' to 9' diameter) steam drum 22 and thereafter over two large driven internally water cooled chill rolls 23 before being passed over a second set of printing-impression rollers (not shown) and through a second dryer similar to that shown in FIGURE 2. Outside the circumference of the steam drum. 22, and covering the web 20 between the rollers 21 and 23, there is provided an arcuate hood 24 covering a set of spaced nozzles 25 for directing jets of hot air against the web 20 and, alternating with said jets, exhaust or vent inlets 26 for exhausting the hot air.

The hot air is supplied to the nozzles through a duct 27, the air being heated by means of a burner 28 and impelled by means of a fan 29. The exhausted air is withdrawn from the inlets 26 through a duct 30 having a first branch 31 leading to the burner 28 for recirculating a part of the hot air and a second branch 32 having a fan 33 for venting another part of the hot air. A damper 33 at the throat formed where the two ducts 31 and 32 join maybe adjusted to vary the ratio of recirculated to vented hot air.

In the dryer of FIGURE 2, the surface temperature of the steam drum 22 is about 340 F.; the hot air is supplied at 350 F. to 700 F.; the web exit temperature is upwards of 350 F. The air exit velocity at the nozzles 25 may be either 4000 to 8000 f.p.m. (specifically, 5000- 6000 f.p.m.) or 10,000 to 17,000 f.p.m. In the case of the lower air velocity, the nozzles are of round cross sectional form; in the case of the 10,000 to 17,000 f.p.m. air velocity the nozzles take the form of slots. The web 20 speed may be 1000 to 1500 f.p.m. when the hot air is supplied at low velocity, or 1500 to 2000 f.p.m. when the air is supplied at high velocity.

In the high velocity hot air dryer of FIGURE 3 the printed paper web 34 passes from a first set of printingimpression cylinders (not shown) first over a small internally water cooled support idler roller 35, through a dryer hood indicated at 36 optionally including additional water cooled idler support rollers 37 and thereafter over large internally water cooled chill rolls 38. Thereafter the web passes to a second set of printing-impression rollers (not shown) and through a second dryer essentially identical with that of FIGURE 3. Within the hood 36 there are provided spaced upper and lower air nozzles 39 which direct jets of hot air against both surfaces of the web 34. This air is vented through exhausts 40 provided between the nozzles 39. The air from these exhausts moves through ducts 41, a part being vented through a duct 42 having an exhaust fan 43 and another part being recirculated through a duct 44 leading to the nozzles 39 and having a burner 45 for heating the air and a fan 46. A damper 47 may be adjusted for varying the ratio of recirculated air to vented air.

In the dryer of FIGURE 3, the air temperature ranges from 350 F. to 600 F. and the web 34 exit temperature ranges upwardly from 300 F. The air velocity at the nozzles is 10,000 to 15,000 or 17,000 f.p.m. The web speed may range from 1500 to 2000 f.p.m.

In the description of FIGURES 1 through 3, reference has been made to printing one side of the webs immediately ahead of the dryers by means of single sets of printing-impression cylinders followed by printing on the other side and drying of the then deposited ink. Such printing, of course, is black on white letterpress printing, and the above reference has been made solely to simplify the description of the dryers. The latter are also used, as is well known, to dry webs subjected to simultaneous printing on both sides by offset methods and to multicolor letterpress or offset printing in which inks of several colors have been deposited on the paper web in rapid succession and without drying the ink before the next impression is made. Such multicolor printing may involve a single impression cylinder and several printing cylinders associated therewith, or it may be done by means of successive sets of printing-impression cylinders. Since ordinarily more ink is deposited on the paper in four color printing, it is obvious that four color printing is likely to be more troublesome, from the standpoint of condensate streaking than black on white printing, and therefore the present invention is of particular utility when applied to four color printing.

It will be noted that in the dryers of FIGURES 1 through 3 there are a number of areas where volatilized ink material may condense and collect. Examples are the chill rolls 19, 23 and 38, the support rolls 12 and 37, the hoods 14 and 15, and the exhaust ducts 14, 15, 16, 17, 30, 41 and 42. In all these areas, surfaces that are contacted by volatilized material are kept at a relatively low temperature, either by Water cooling, as in the case of the rolls, or by contact with the atmosphere, as in the case of the hoods and the exhaust ducts. Further, condensate can collect or accumulate at these locations. The paper web is separated, at high web speeds, from the chill rolls 19, 23, 34 and 38, and from the support rolls 12 and 37, by a cushion or layer of air, and streaking of the web does not occur until suflicient condensed material has accumulated on the roll to bridge the air gap and to streak or spot the web unless, as sometimes happens, the web from time to time bounces into contact with the roll.

In the hoods 14 and 15, and in the exhaust ducts 17, 27, 30, 31, 32, 41 and 44, material can condense and collect until the aggregate mass grows to the point where it will no longer adhere to the wall surface but will drip off and flow or fall onto the paper web. It may be noted that the condensate formed on the water cooled rollers is sometimes solid at room temperature yet generally includes more volatile and less easily condensible material than the condensate formed on the hood and duct walls. The condensate on the support rollers may even be largely ink solvent. The condensate formed on the hood and duct walls tends to include high boiling material of higher melting point which, when condensed, is pasty or solid rather than fluid. Further, this latter condensate is often quite tacky and is therefore apt, when falling onto the paper web, to cause web breaks. It is sometimes referred to as rosin drip.

The tendency to generation of condensate streaks depends, among other things, 1) on the composition of the printing inks and (2) on the conditions prevailing in the printing press and in the dryer associated therewith. The present invention relates to an ink composition which reduces or eliminates condensate streaks, as explained hereinbelow. However, the second factor (printing press and dryer conditions) requires some discussion in order to illustrate the gains made possible by the reduction or elimination of condensate streaks.

Assuming a sufficient heat transfer to the web to effect at least reasonably complete drying, high web speed and heavily inked forms or printing plates tend to cause generation of condensate streaks. Under such opera-ting conditions, large volumes of vapors are generated in the dryer, and these vapors are not removed fast enough from the dryer so that some condensation will take place. A generally accepted expedient for drying when condensate streaks are encountered is to reduce press speed to the point where condensate streaks are largely eliminated. This expedient is not always successful, but it succeeds, if at all, at the cost of severely reducing the productivity of the press. Thus, elimination or reduction of condensate streaks will directly increase the productivity of a heat set rotary printing press.

I have now found that condensate streaks may be greatly reduced or eliminated by printing with inks formulated from conventional ink ingredients according to conventional formulating principles as long as at least 98% of the ink is made up of ingredients which meet the requirement of a test described as follows and utilizing equipment as shown in FIGURE 4.

THE TEST PROCEDURE The test samples are 1 gram. Each sample is placed in an aluminum foil (0.003 thick) round pan 48 that is 2% in diameter and /8 high (Fisher cat. No. 87325, size C). The pan is then covered with a similar inverted pan 49 of known weight formed with a central aperture 50 that is A in diameter. The pans 48 and 49 are each formed with a A2" wide outturned flange 51 so that the superposed pans can be held together by paper clips (not shown). The pans are protected from drafts while heated for one hour on a hot plate 52 having a surface temperature of 610 F. to 630 F. More specifically, I use a Schaar Scientific 3600 watt, c'at. No. G8330, 18" x 24" surface hot plate with all circuits on, and adjusted by means of a 220 volt heavy duty 30 amp. to control the temperature of heating by selecting an area having a surface temperature of 630 F. to 610 F. I use an Alnor 0 F.-1000 F. Thermocon Type 4200A contact pyrometer having a 4040 tip with a self-contained cold junction calibration spot.

By means of this pyrometer a central constant maximum temperature is located on the hot plate surface and its temperature is adjusted to 630 F. Then the temperature range of the hot plate surface, with the exception of a peripheral 4" wide band (which is not used) will be 630 F. to 610 F. In this zone 15 samples can be run simultaneously. To insure good contact a steel screen 53 is placed on top of the pans. This screen is coarse enough so that none of the V openings is even partially blocked. The sample pans are huddled on the central calibrated area Without contacting each other. The area of screen contact with the pans is minimal so that the screen does not act as a cooling drain or heat sink.

The hot plate is brought to its desired high temperature and kept there for a few hours before the samples are placed thereon. After an hour of heating the pans are re moved and cooled. The inverted collection pans 49 are weighed, and the weight gain for the inverted collection pan is noted and the amount of condensate collected is computed as percent of the original sample.

Preferably, the determination of condensate collected is run in triplicate. If one result varies widely from the other two, the one must be disregarded. According to the standard of the present invention, at least 98% of the ink must be made up of ingredients that yield not more than 6% collected condensate as determined by the above described test procedure.

Specifically, this test is applied to each and every ingredient, and not to mixtures of some ink ingredients, nor to finished inks. There are some finished complete inks that when tested yield less than 6% of collected condensate but still tend to form condensate streaks, although other inks having such low condensate yields do not. But finished complete inks that yield more than 6% collected condensate do tend to form condensate streaks. The same is true of mixtures of ink ingredients such as pigment flushes which ordinarily include pigments, varnishes and surface active components. These flushes, constituting pigment plus vehicle, are normally used in an amount of at least about 2% of the ink. There is no practical reason to use more than about 60%. A pigment flush may yield less than 6% collected condensate although one or more components yield more than 6%. A flush containing such components should not be used in making the inks of this invention regardless of the low collected condensate value obtained when this flush is tested if as a result of such use the finished ink would contain more than 2% of ingredients yielding more than 6% condensate. Neither should a flush be used that when tested yields more than 6% collected condensate.

Conventional ink ingredients that yield more than 6% collected condensate may not be included in inks according to the present invention in a total amount exceeding 2%. Examples of such conventional ink ingredients are wood rosin, gum rosin, dimerized rosins, calcium and zinc rosin salts, rosin esters such as the pentaerythritol ester, coumarone-indene resins, copolymers of methyl styrene and vinyl toluene, linseed oil-phthalic anhydride esterified with pentaerythritol, polyurethane, many linseed oil and linseed oil varnishes, bodied soya oil, dehydrated castor oil, stearic acid, aluminum stearate, lanolin, lecithin, petrolatum, methyl violet toner containing fatty acids, alkali blue toner containing linseed oil, highly resinated toners and lakes, and pigments and lakes flushed in linseed and other varnishes.

Examples of ink ingredients yielding 6% or less collected condensate are given below.

Resins include most high grade Gilsonites; Inkovar 180 (a Pennsylvania Industrial Chemical Corporation cyclopentadiene type heat polymer having a minimum ball and ring softening point of 177 C., an acid number of less than 1, and soluble in a typical gravure solvent of at least 55% solids at 20 C.) Pentalyn X (a Hercules maleic modified pentaerythritol ester of rosin soluble in aliphatic and aromatic hydrocarbons); Pentalyn 802A and Pentalyn 833 (-both Hercules phenolic-modified pentaerythritol rosin esters partly soluble in petroleum hydrocarbons); Arochem 605 (an Archer-Daniels-Midland pentaerythritol ester of fumaric and maleic ester soluble in aliphatic hydrocarbons); polycarbonates; phenoxy resins; methyl methacrylate resins; polysulfone resins; and polyphenylene oxide resins.

Drying oils that may be used include some polymerized linseed oils, bodied wood oil and bleached safliower oil.

Certain gloss varnishes (which are reaction products and not simple solutions or mixtures of ingredients) may also be used in preparing the inks of the present invention. Many available gloss varnishes, however, yield more than 6% collected condensate. I therefore give below directions for making gloss varnishes that yield 6% or less collected condensate.

The following gloss varnishes are prepared under a blanket of nitrogen or carbon dioxide, preferably in a stainless steel kettle, with smooth, adequate agitation and evenly applied heat.

Gloss varnish N0. 1

239 parts polymerized linseed oil, 60 parts pentaerythritol and 0.15 part Ca(OH) or PbO catalyst are reacted. Specifically, while the linseed oil is heated at 480 F. one half of the pentaerythritol is added. After 10 minutes, or when a clear liquid has been formed, the remaining pentaerythritol is added. After 40 additional minutes of heating the reaction is reasonably complete. One milliliter of the product should be soluble in 3 /2 milliliters anhydrous methanol at room temperature. The final acid number should be less than 10.

The above reaction product is further reacted as follows. 39 parts reaction product, 20 parts dimerized rosin, 10.2 parts pentaerythritol, 20.1 parts isophthalic acid, 0.8 part maleic anhydride and 0.9 part fumaric acid are heated together and gradually raised to 560 P. where the mixture is held until an acid number of less than 10 is reached. Usually 4 to 6 hours are required. The resulting gloss varnish must yield less than 6% collected condensate.

Gloss varnish. N0. 2

parts rosin are melted in a kettle. While the molten rosin is being stirred, 4 parts fumaric acid and 2 parts maleic anhydride are added. 0.1 part phosphoric acid is then slowly added. Heating at 400 -F. is continued for 2 hours. The temperature is gradually raised to 560 F. while 11 parts pentaerythritol is gradually added. Heating at 560 F. is continued for about 6 hours until the reaction is complete and the acid number is 10 to 15. The product should yield less than 6% collected condensate.

Pigments and extenders that may be used include chrome yellow, phloxine toner, lithol rubine, cyan blue, peacock blue, channel black, furnace black, phthalocyanine blue and green, toluidine red, chrome or milori green, chrome orange, iron blue, clay, aluminum hydrate, blanc fixe, calcium carbonate, magnesium oxide and titanium dioxide.

Solvents that may be used include the usual aliphatic and aromatic hydrocarbon solvents included in heat set printing inks. The usual petroleum fractions are conventionally identified by the boiling point of the first 5% fraction, e.g. 440 oil or 470 oil. Very high boiling petroleum fractions such as are used in formulating news inks (boiling point 650 F. or higher) yield excessive amounts of collected condensate and should not be included with the inks of this invention except as a part of the total 2% of allowable high collected condensate material.

Additives are materials included with printing inks to influence properties such as body, viscosity, gelling, scuff resistance, rub or smear resistance, gloss, toughness and ink trapping. Examples of additives that may be used are aluminum octoate and calcium stearate which yield less than 6% collected condensate. Some additives yielding more than 6% collected condensate may be used in amounts ranging up to 2% of the ink. Thus, polyethylene of about 2,000500,000 molecular weight may be used in the form of a wax compound made up of 15% polyethylene, 42.5% Inkovar 180 or other resin yielding less than 6% collected condensate, and 42.5% solvent such as 470 oil.

Examples of specific ink formulations are given as follows:

Example 1.-Black letterpress ink Percent Furnace black 18.4 Clay 11.7 Alumina hydrate extender 1.1 Gilsonite 24.1 470 oil 44.7

Example 2.-Black letterpress or web olfset ink Percent Ohannel black 13.3 Polyethylene wax compound 4.2 Gloss varnish 6.2 Inkovar 180 18.2 Gilsonite 9.2

440 oil 46.8

Toner 2.1

Example 3.Red letterpress ink Percent Phloxine red 15.7 Polyethylene wax compound 4.3 Gloss varnish 6.1 Inkovar 180 30.0 470 oil 43.9

Example 4.--Red letterpress or Web offset ink Percent Lithol rubine 13.1 Polyethylene wax compound 5.0 Gloss varnish 15.8 Inkovar 180 21.3 500 oil 44.8

Example 5.-Yellow letterpress or web ofiset ink Percent Benzidine yellow 9.9 Chrome yellow 19.8 Inkovar 180 20.8 Gloss varnish 13.1 Polyethylene wax compound 4.0 470 oil 32.4

Example 6.Yellow letterpress or web otfset ink Percent Chrome yellow 23.1 Gloss varnish 37.2 Polyethylene wax compound 4.8 470 Oil 34.9

Example 7.Blue letterpress or web offset flush or concentrate Percent Pht-halocyanine blue 26.1 Phthalocyanine green 2.6 Inkovar 180 varnish (60% /470 oil) 39.1 Gloss varnish (60%/470 oil) 25.2 470 oil 7.0

Example 8.Blue letterpress ink Percent Peacock blue 8.2 Phthalocyanine blue 0.8 Inkovar 22.2 Gloss varnish 16.7 Polyethylene wax compound 6.1 470 oil 46.0

Example 9.Blue letterpress or web offset ink Percent Phthalocyanine blue 7.3 Phthalocyanine green 0.8 Inkovar 180 21.3 Gloss varnish 18.4 Polyethylene wax compound 3.5 470 oil 48.7

The above inks can be made by any conventional method, as by stirring the ingredients together and then passing the resulting mixture through an ink mill. Or the gloss varnish and/ or resin dissolved in solvent can be used to flush the pigment to form a concentrate (as in Example 7) which is then diluted with solvent to make the finished ink.

It should be noted that for the purpose of the present invention each one of the inks used in multicolor printing must meet the requirements herein stated, and that the same applies to the inks used on the opposite sides of a paper web, since otherwise condensate streaking will take place. Obviously, any one ink laid down on a paper web can cause condensate streaking on this web, regardless of what other inks may also be laid down on this web. Further, condensate streaking may be due to the cumulative effect of several inks deposited on a paper web, even though conceivably each ink, laid down by itself, would not cause condensate streaking. Some conventional inks cause condensate streaking under all except the most favorable conditions. Other conventional inks do not cause condensate streaking except under adverse conditions such as high web speed, excessive general or local dryer temperatures, heavy forms, low cooling water temperature, low ambient temperature and/ or the presence of other inks tending to form condensate streaks. The inks of the present invention, on the other hand, do not form condensate streaks even under the above noted adverse conditions, or in any case can tolerate much more adverse conditions than conventional inks.

The inks of the present invention are generally characterized by good release of relatively low boiling solvents such as 440, 470 and 500 oil, which are the preferred solvents. Therefore, the solvent content of the ink is released quickly and early in the drying process, so that the resulting vapors are evacuated rapidly from the dryer and are not carried along to the cool and chilled roller surfaces where they would be condensed. Thus the present invention serves to reduce or eliminate the wetting of the paper web with condensed solvent which would resoften the dried ink.

All amounts, parts and percentages herein are by weight.

Having described my invention as related to the embodiments set out herein, it is my intention that the invention be not limited by any of the details of description, unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

I claim:

1. In a method of continuously printing on a moving paper web with a heat setting ink including the step of passing the freshly printed web through a heat setting 9 10 zone having relatively cool areas, the improvement comwith a successive series of inks prior to said heating to prising: printing on said web without producing substanheat set all said inks. tial condensate streaking with a substantially condensate free ink comprising a hydrocarbon soluble film forming References Clted resinous binder, a hydrocarbon solvent therefor, pigment 5 UNITED STATES PATENTS material, and additives for controlling the printing prop- 2 972 303 2/1961 De Marchi et a1. erties of Said ink, at least 0f Said ink being made Bernardi et 1.

up of ingredients each yielding less than 6% condensate when measured by the method of The Test Procedure de WILLIAM B. PENN Primmy E j scribed in the specification hereof; and heating said 10 printed web to heat set the ink. US. Cl. X.R.

2. The method of claim 1 wherein said web is printed 101-426

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